Editing a Real Dog to Talk
I guess this largely depends on the amount of realism you're going for...

If you're going for something hyper-realistic like what you see in movies like Cats&amp;Dogs, then you will probably have to model part of your dog's face in Blender and try to match materials and lighting to the footage. That model can then be parented to motion trackers so it matches the movements of your dog (and possibly the camera).

Another, more lo-tech approach would be to take existing footage of your dog opening and closing her mouth and then simply retiming/reediting that footage to match a voice track using Blender's VSE.

Yet another approach might be to distort/morph/warp the footage to give the appearance of your dog opening and closing her mouth in sync to the voice track but: A. I wouldn't know off the top of my head how to do that in Blender (or if it is possible at all - though I suspect it is) and B. the end result would probably look nowhere near as convincing as the first two approaches.